Hydropower refers to the power that is obtained from the energy of falling and fast running water. It is a renewable energy source which can be used for irrigation and the operation of various mechanical devices including gristmills, sawmills, trip hammers, textile mills, domestic lifts and ore mills. It is also used to produce hydroelectricity. Hydroelectric power plants can have a reservoir through which the energy of falling water can be converted into electricity. The kinetic energy of running water can also be converted into electricity through run-of-the-river hydroelectricity generation plants. Another form of electricity generation through hydropower is through tidal stream generators which make use of tidal power from oceans and rivers. This book presents the complex subject of hydropower in the most comprehensible and easy to understand language. It provides comprehensive insights into this field. This book is an essential guide for both academicians and those who wish to pursue this discipline further.